1/*
2 *  linux/mm/page_io.c
3 *
4 *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
5 *
6 *  Swap reorganised 29.12.95,
7 *  Asynchronous swapping added 30.12.95. Stephen Tweedie
8 *  Removed race in async swapping. 14.4.1996. Bruno Haible
9 *  Add swap of shared pages through the page cache. 20.2.1998. Stephen Tweedie
10 *  Always use brw_page, life becomes simpler. 12 May 1998 Eric Biederman
11 */
12
13#include <linux/mm.h>
14#include <linux/kernel_stat.h>
15#include <linux/pagemap.h>
16#include <linux/swap.h>
17#include <linux/bio.h>
18#include <linux/swapops.h>
19#include <linux/writeback.h>
20#include <asm/pgtable.h>
21
22static struct bio *get_swap_bio(gfp_t gfp_flags, pgoff_t index,
23				struct page *page, bio_end_io_t end_io)
24{
25	struct bio *bio;
26
27	bio = bio_alloc(gfp_flags, 1);
28	if (bio) {
29		struct swap_info_struct *sis;
30		swp_entry_t entry = { .val = index, };
31
32		sis = get_swap_info_struct(swp_type(entry));
33		bio->bi_sector = map_swap_page(sis, swp_offset(entry)) *
34					(PAGE_SIZE >> 9);
35		bio->bi_bdev = sis->bdev;
36		bio->bi_io_vec[0].bv_page = page;
37		bio->bi_io_vec[0].bv_len = PAGE_SIZE;
38		bio->bi_io_vec[0].bv_offset = 0;
39		bio->bi_vcnt = 1;
40		bio->bi_idx = 0;
41		bio->bi_size = PAGE_SIZE;
42		bio->bi_end_io = end_io;
43	}
44	return bio;
45}
46
47static int end_swap_bio_write(struct bio *bio, unsigned int bytes_done, int err)
48{
49	const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
50	struct page *page = bio->bi_io_vec[0].bv_page;
51
52	if (bio->bi_size)
53		return 1;
54
55	if (!uptodate) {
56		SetPageError(page);
57		/*
58		 * We failed to write the page out to swap-space.
59		 * Re-dirty the page in order to avoid it being reclaimed.
60		 * Also print a dire warning that things will go BAD (tm)
61		 * very quickly.
62		 *
63		 * Also clear PG_reclaim to avoid rotate_reclaimable_page()
64		 */
65		set_page_dirty(page);
66		printk(KERN_ALERT "Write-error on swap-device (%u:%u:%Lu)\n",
67				imajor(bio->bi_bdev->bd_inode),
68				iminor(bio->bi_bdev->bd_inode),
69				(unsigned long long)bio->bi_sector);
70		ClearPageReclaim(page);
71	}
72	end_page_writeback(page);
73	bio_put(bio);
74	return 0;
75}
76
77int end_swap_bio_read(struct bio *bio, unsigned int bytes_done, int err)
78{
79	const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
80	struct page *page = bio->bi_io_vec[0].bv_page;
81
82	if (bio->bi_size)
83		return 1;
84
85	if (!uptodate) {
86		SetPageError(page);
87		ClearPageUptodate(page);
88		printk(KERN_ALERT "Read-error on swap-device (%u:%u:%Lu)\n",
89				imajor(bio->bi_bdev->bd_inode),
90				iminor(bio->bi_bdev->bd_inode),
91				(unsigned long long)bio->bi_sector);
92	} else {
93		SetPageUptodate(page);
94	}
95	unlock_page(page);
96	bio_put(bio);
97	return 0;
98}
99
100/*
101 * We may have stale swap cache pages in memory: notice
102 * them here and get rid of the unnecessary final write.
103 */
104int swap_writepage(struct page *page, struct writeback_control *wbc)
105{
106	struct bio *bio;
107	int ret = 0, rw = WRITE;
108
109	if (remove_exclusive_swap_page(page)) {
110		unlock_page(page);
111		goto out;
112	}
113	bio = get_swap_bio(GFP_NOIO, page_private(page), page,
114				end_swap_bio_write);
115	if (bio == NULL) {
116		set_page_dirty(page);
117		unlock_page(page);
118		ret = -ENOMEM;
119		goto out;
120	}
121	if (wbc->sync_mode == WB_SYNC_ALL)
122		rw |= (1 << BIO_RW_SYNC);
123	count_vm_event(PSWPOUT);
124	set_page_writeback(page);
125	unlock_page(page);
126	submit_bio(rw, bio);
127out:
128	return ret;
129}
130
131int swap_readpage(struct file *file, struct page *page)
132{
133	struct bio *bio;
134	int ret = 0;
135
136	BUG_ON(!PageLocked(page));
137	ClearPageUptodate(page);
138	bio = get_swap_bio(GFP_KERNEL, page_private(page), page,
139				end_swap_bio_read);
140	if (bio == NULL) {
141		unlock_page(page);
142		ret = -ENOMEM;
143		goto out;
144	}
145	count_vm_event(PSWPIN);
146	submit_bio(READ, bio);
147out:
148	return ret;
149}
150